Bars which have a pH of between 5 and 8 and which are optically transparent (e.g., optically clear in that light is transmitted so that a body lying on the opposite side is entirely visible) are highly desirable.
Bars have previously been made using fatty acyl amino acid surfactants, for example, alkyl glutamates. Alkyl glutamates have a structure as follows:
                wherein R is straight or alkenyl group having 6 to 24 carbons; and M is an alkali or alkaline metal, typically sodium or potassium, or trialkanolamine.        
As noted, a number of references disclose use of such fatty acylamino acids in bars. U.S. Pat. No. 3,663,459 to Yoshida et al., for example, relates to detergent bars comprising water soluble salts of N-acyl-glutamic acids and N-acyl aspartic acids. The bars are opaque in appearance. U.S. Pat. No. 4,273,684 to Nagashima et al. discloses transparent bars containing basic amino acid salt of N-long chain acyl optically active acidic amino acid. U.S. Pat. No. 5,098,608 to Miyazawa discloses transparent solid detergent compositions containing N-acyl acidic amino acid salts.
JP 8291123 to Lion Corp. discloses certain types of surfactant structures similar to those of the subject invention. There is no disclosure of the compounds, however, in bar compositions and it is unpredictable that use of such compounds in bars would lead to optical transparency.
It would be greatly desirable to find molecules, other than those currently used, which could be used in bar compositions to provide a combination of optical transparency and pH neutrality (i.e., pH 5 to 8). Unexpectedly, applicants have found specific molecules which obtain these objectives.